Multicolor flow cytometry has become a powerful tool in many areas of research, and UC Davis has been at the forefront of this technology since 2000. With the development of the first custom designed 12-color, 14 parameter MoFlo Cell Sorter, UCD investigators have been developing multi-color panels for research. This research has generated over 250 publications and more than 200 NIH grants, including 57 NIH grants this year alone. The UCD Opticore was formed in 1995 on the Davis Campus, expanded to the NCI designated Cancer Center in Sacramento in 2002, and expanded again in 2006 to a second Sacramento location in collaboration with the new Stem Cell Program. The Sacramento facilities are accessible to a wide range of programs, including the UCD Medical Center, the MIND Institute, the Stem Cell Program, and the Cancer Center. Currently, 26 NIH grants based at UCD-Sacramento are dependent on access to a multi- parameter flow cytometer. However, these projects are limited to the use of a cell sorter, which was purchased for the Stem Cell Biology program. This sorter requires a dedicated operator, is already at greater than 50% user capacity and continuing to grow only a year after the facility opening. The acquisition of a self-operated, multi-parameter analytical flow cytometer will be critical to the success of the 26 NIH-funded research programs, many of which do not require cell sorting on a routine basis. The LSR-II cytometer is the only benchtop analysis instrument with five laser capability and the capacity to acquire up to 18 parameters, including 16 different fluorochromes, with additional capacity for future expansion. This state-of-the-art instrument will allow us to readily transfer the analytical panels already developed, plus add the additional applications and fluorochromes required for specific research programs as described in this application. Placing the instrument in the Optical Biology Core facility will ensure that the instrument is carefully maintained, and investigators will have maximum access to flow cytometry instrumentation and expertise.